Propellent explosive



Patented Jan. 16, 1934 STATES,

TENT; FFECE PROPELLENT EXPLOSIVE Great Britain No Drawing. Application January 6, 1931, Serial No. 507,041, and in Great Britain January 6,

12 Claims.

This invention relates to the manufacture of propellent explosives, and has for its object the prevention of metal fouling in the bore of guns or rifles.

- It is well known that both small arms and ordnance sufier during use from what is known as metallic fouling. In the case of small arms this is due to the deposition on the bore of metal or metallic alloy such as cupro nickel derived from the envelope of the bullet; in the case of larger guns it is due to copper or alloy of copper derived from the driving band of the projectile. This separation and deposition of metal or alloy takes place on account of the high temperature within the barrel and the friction between the soft metal and the wall of the barrel.

The fouling accumulates rapidly and is objectionable, since it reduces the bore of the rifle or gun, and may in consequence cause the development of high pressure. In any case it seriously interferes with the accuracy of firing, and greatly reduces the life of the rifle or gun.

In order to avoid this deposition it has been proposed to insert metallic tin or an alloy of 2 tin and lead immediately behind that portion of the projectile which causes the metallic fouling. This has been efiected in various ways such as by placing a ring of tin or alloy of tin in a groove in the body of the projectile behind the 80 copper driving band, or in any other suitable position where it is subjected to the heat developed by the combustion of the powder, or by introducing it in the form of metal foil into the cartridge case between the firing charge and the projectile 5 or even in the charge of powder itself.

Further, metallic tin, an alloy of tin, or a compound of tin such as tin oxide, in finely divided condition, may be incorporated in the powder during manufacture. The advantage claimed for this method is that it ensures a more uniform distribution of the metal, or alloy, or compound, and causes it to be more uniform in effect. The small amount of metallic fouling which may be produced even inthe presence of tin is, under these conditions, more uniform and interferes less with the accuracy of the firing.

The action of tin or tin alloys, or tin compounds in removing metallic fouling and preventing its accumulation has been explained by 0 the suggestion that the metallic tin is deposited upon the bore of the gun and alloys itself with the eroded copper or alloy which forms the metallic fouling, yielding an alloy which is brittle and.

does not adhere to the steel of the barrel, or,

alternatively, an alloy with a relatively low fusion point. Such alloys are swept out of the barrelwith the powder gases instead of remaining fixed to the steel.

An additional advantage of the incorporation of tin or an alloy of tin or a tin compound is that the fiash produced by the combustion of the powder gases at the muzzle is very considerably reduced.

In addition to metallic tin, alloys not only of tin with lead, but also those including zinc have been proposed.

Now, when the finely-divided tin or alloy is incorporated with a smokeless powder the dim-- culty met with is that of mixing a small quantity of a fine powderof relatively high density uniformly with the other constituents of the-powder. As explained below, in accordance with our invention, we employ organo-metallic compounds in place of metals. By the term organo-metallic compounds is meant a compound in which the metal is directly linked to carbon.

When tin is added in the form of an organometallic compound, it has been found to be more effective in reducing fouling than when introduced in the metallic form. It is thus possible to reduce the amount of tin actually present in the propellent charge by introducing it in the form of an organo-metallic compound.

The organo-metallic compound used must possess a. sufilciently low volatility to guarantee its retention in the powder for an indefinite time, high chemical stability so that it does not decompose on storage and possibly give rise to constituents that are detrimental to the life of the powder, and no destabilizing action on the con- 0 stituents of the powder. A compound of the above properties, when incorporated in the powder gives the desired freedom from metallic fouling and diminution of muzzle fiash. Such a substance is tin tetra-phenyl or tetra-phenyl-stannane, Sn(CsH5) 4, a crystalline compound melting to 224-225 C. and less than 0.5% soluble in ether, alcohol, or ether-alcohol mixtures.

The organo-metalic compounds may also be used in solution in the volatile solvent when the 1 propellent is of the type requiring a volatile solvent for its manufacture. An example of such a. compound is tin tetra-butyl or tetra-n-butyl stannane, Sn(C4H9)4, a ,clear liquid boiling at 150 C. at an absolute pressure of 6 mm. of mercury and having a specific gravity of about 1.1. Its volatility iss'uch that a thin film loses on evaporation at 60 C. only 2.6% of its weight in three hours. It is very stable to atmospheric influence and ordinary chemical reagents such as il water, dilute acids and salts, and far from having a destabilizing action on nitrocellulose, appears to possess stabilizing properties. It is readily soluble in the volatile solvents usually employed in the manufacture of smokeless powder, such as a mixture of ether and alcohol, or acetone;"it is practically insoluble in water and is non-hygroscopic. 1

Where compounds dissolved in solvents are used, density is not a matter of importance, so that there is a wider range of compounds available. We also find that the invention is of particular use in rifle nitrocellulose military powders employing tin organo-compounds which are soluble in solvents used.

The invention consists in the incorporation into propellent explosivesof organo-metallic compounds, preferably of tin. These have a density approximating to that of the remaining constituents of the explosive. v

The'invention also consists in a process according to the preceding paragraph in which there are employed organo-metallic compounds that are insoluble or only slightly soluble in the solvents oringredients. By the use of such compounds of a density about equal to that of the several ingredients, greater regularity of dispersion is obtained.

The invention also consists in a modification of the process according to the preceding paragraph in which there are employed organo-metallic compounds which are applied in solution in the solvents or ingredients, whereby they become distributed in the molecular state.

The invention also consists in processes relating to the manufacture of propellent explosives substantially as herein described, and in explosives which may be thus produced, particularly rifle nitrocellulose military powders containing tin organo-compounds which are soluble in thesolvents employed in the manufacture of the powders.

The invention may be carried into effect as shown in the following examples:-

(1 Non-solvent powder (2) Nitrocellulose powder This is an example more particularly of a rifle nitrocellulose powder.

The nitrocellulose or mixture'of nitrocelluloses is dehydrated with alcohol and placed in an incorporating machine, the requisite amount of ether or ether-alcohol mixture, containing in solution 3% of tetra-n-butyl-stannane with 1% of diphenyl-amine, being added. The mixture is incorporated, pressed, cut and finished in the manner normally employed. The powder may, if necessary, be surface moderated.

(3) Nitroglycerine powder This is an example of a cordite powder, which may be employed as a military small arms powder. To 36 parts of guncotton to which have been added 58 parts of nitroglycerine are incorporated with the requisite amount of acetone in which have been dissolved 3 parts of tri-n-butyl propyl stannane, (C4H9)3SI1(C3S7), 3 parts of mineral jelly are added and mixing is continued. The dough is extruded from a press and dried in the usual way.

The following compositions are representative of the three types of powder:-

(1 Non-solvent powder Type (1) is a so-called non-solvent powder in which no volatile solvent or gelatinizer is generally employed. A small proportion of acetone or other volatile solvent, rarely exceeding 5% of the total weightv of the batch, is occasionally incorporated with the mixture of the ether constituents to facilitate the gelatinization of the nitrocellulose on the hot rolls through which the material passes before it reaches the pressing and extrusion stage. A powder so prepared is generally, however, called a non-solvent powder to distinguish it from the powders of the older cordite type in the manufacture of which from 20% to 40% of acetone, calculated on the total weight of the batch is used.

The homogeneous mixing of metals, such as tin, lead and zinc or alloys of tin or lead or zinc or compounds of the same metals, with other constituents of much smaller specific gravity is difficult. We prefer, therefore, in powders of this type, to use organo-metallic compounds alone, and not to mix them with such metals, alloys or compounds.

Type (2) is a nitrocellulose powder prepared as outlined above. The solid or liquid organometallic compound or compounds may be mixed with metallic tin, lead or zinc or alloys of these metals or compounds of these metals.

The remarks applied above to type (2) also apply to type (3) nitroglycerine powders of the cordite variety.

The invention is not restricted to the use of ingredients in the proportions shown, nor to the use of these ingredients only, nor to any particular method of mixing or incorporating the ingredients. various nitrated alcohols, such as nitro glycol,

Thus various types of nitrocellulose,

various stabilizers, various solvents or solvent mixtures, and, in the case of powders prepared without the use of volatile solvent; various gelatinizers may be used. In addition to the ingredients mentioned, other nitrated bodies, such as dinitrotoluol or the usual surface moderants may be present in the finished product.

The tin compound may be added to the charge of powder before or during its gelatinization, as even if the tin compound is not completely soluole in the mixture. the advantage of uniform distribution will not thereby be sacrificed, since the specific gravity is much less than that of metallic tin, and preferably approximates to that of the other constituents of the powder.

- The invention is not limited to any particular organo-metallic derivative of tin or other metal, but any solid or liquid stable and substantially non-volatile organo-metallic derivative may be used. By aslight adjustment of web thickness of the powder grain, the required charge to give corresponding ballistics can be obtained when the same weight of powder charge is used as can be obtained from a powder not containing the organo-metallic compound, that is to say, by increasing the size of the perforations, a larger igniting surface may be employed where necessary.

Variations in the composition of the powders may be made in accordance with the size of gun in which they are to be used.

As many apparently widely different embodiments of this invention may be made without departing from the spirit thereof, it is to be understood that we do not limit ourselves to the foregoing examples or descriptions except as indicated in the following patent claims.

We claim:

1. A propellent explosive containing as an ingredient a stable, non-volatile organc-metallic tin compound in which the metal is linked directly to carbon and which has no destabilizing action on the constituents of the powder.

2. The product of claim 1 in which the organemetallic compound is only slightly soluble in the solvents and ingredients of the explosive.

3. The product of claim 1 in which the organometallic compound is insoluble in the solvents and ingredients of the explosive.

4. The product of claim 1 in which the organometallic compound is soluble in the ingredients of the explosive.

5. The product of claim 1 in which the organometallic compound is tetra-n-butyl stannane.

6. The product of claim 1 in which the organometallic compound is tetra-phenyl stannane.

'7. The product of claim 1 in which the organometallic compound is a compound of tin with a hydrocarbon radicle.

8. The process of manufacturing propellent explosives which comprises incorporating with the explosive ingredients a stable and substantially non-volatile organo-metallic tin compound.

9. The process of claim 8 in which the organometallic compound is a compound of tin .with a hydrocarbon radicle.

10. The process of claim 8 in which the organometallic compound is tin tetraphenyl.

11. The process of claim 8 in which the organo-' metallic compound is tin tetrabutyl.

12. The process of claim 8 in which the organometallic tin compound is an. plied in solution in the solvents and ingredients of the explosive composition.

ROBERT BURNS.

OLIVER WARD S'I'ICKLAND.

Certificate of. Correction Patent Nb. 1,943,421.

ROBERT BURNS ET AL.

January 16, i934.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correctionas follows: Page 2, line 79, for

read (0 117 Sn(O' H and that the said Letters Patent should be read with the correction therein that the same Ina Patent Oflice.

Signed *and sealed this 20th day of March, A. D. 1934.

[SEAL] y conform to the record of the 'case in the 

